Growth of Southern Pines in Silvopastoral Practices

1. Growth of southern pines at different stand configurations in silvopastoral practices Adrian Ares, David K. Brauer, David M. Burner and Daniel H. Pote Dale Bumpers Small Farms Research Center Agriculture Research Service U.S. Department of Agriculture

2. Tree growth in agroforestry (AF) stands • Lack of reliable growth and yield data for AF practices can make economic predictions uncertain and hinder adoption • Growth models for forests may not apply to AF systems because of spacing and configuration effects

3. Single-row configuration Double-row configuration

4. Some research approaches • Constant initial stand density Varied: Configuration (S, D, T, Q-row) Alley width Distance between trees within rows • Constant alley width Varied: Configuration Initial stand density Distance between trees within rows • Comparison with stands/plots planted in forest-type arrangements

5. Location of pine agroforestry studies Gulf of Mexico

6. 45 yr-old AF stand in Georgia

7. Basal area and livestock gains 731 trees/ha 262 trees/ha Drawn from Lewis et al., 1985

8. Basal area and canopy cover

9. Northern Florida, slash pine, 1135 trees/ha

10. Central Florida, slash pine, 1135 trees/ha

11. Central Louisiana, 18 yr-old stands, 1165 trees/ha 6.7-m alley 15.2-m alley

12. Western Arkansas, 11-yr-old loblolly pine stands,1541 trees/ha Configuration Spacing Basal area (m2/ha) 2002 2003 2004 Double- (1.20 x 2.40) 7.20 m 22.9 28.4 33.4 row Quadruple- (1.20 x 2.40) 16.0 m 19.1 23.3 27.5 row

13. Central Arkansas, 18-yr-old loblolly pine stands,14.6-m alley width

14. Central Arkansas, 18-yr-old Comparisons between loblolly pine basal area in silvopastures and adjacent forests Western Arkansas, 11-yr-old

15. Conclusions • Stand basal area in silvopastures appear to equal or surpass that of forest stands • Research favors single and double-row configurations in silvopastures • Other aspects of silvopastures such as biomass partitioning, bole diameter distribution and wood quality deserve further examination

16. Biomass partitioning

17. Carbon partitioning to tree components is linked to timber production, tree function and ecosystem C stores • Patterns of C partitioning extensively studied in loblolly pine in natural stands and plantations but not in AF systems • AF configurations may greatly modify biomass partitioning

18. Sampling design N Single Double Quadruple (308 trees/ha) (568 trees/ha) (932 trees/ha) 14.6 m 14.6 m 2.1 m 2.4 m 2.4 m Sixty sampled trees(3 per row x 5 rows x 2 pruning x 2 replicates) Felled trees separated into stem, branch, twigs (< 2 cm in diameter) and foliage

20. Tree characteristics in different configurations

21. Effects of configuration on biomass partitioning

22. Biomass in tree components 12.5% 8.1% 30.3% 23.6% 62.8% 51.3%

23. Biomass partitioning in silvopastures and forests Configuration Row Age Stocking % partitioning to yrs trees/ha Bole Branches Foliage Single- 18 308 51.5 35.8 12.7 row Double- 1 18 568 54.0 36.1 9.9 row 2 59.1 29.4 11.5 Quadruple- 1 18 932 58.2 32.3 9.5 row 2 62.5 28.9 8.6 Adjacent 19 983 79.0 18.8 2.2 forest Ku and 18 n/a 83.1 13.5 3.4 Burton (1973) 18 81.6 14.9 3.5 This study

24. Conclusions • Considerable extent of ontogenetic control in loblolly pine in AF plantations • Differences up to 11% in biomass partitioning to stems and up to 7 % to branches • Possible need for allometric functions for agroforestry pine stands (e.g., single, double-row configurations)

25. Wood quality in AF stands ?

26. Acknowledgments • Earl Hardin, Tammy Horton, Jim Misner, Mike Rogers and Jim Whiley for technical assistance • Roy Clardy, Teri Clason, Paul Eberhard, David Haywood, Cliff Lewis, Henry Pearson, USDA Forest Service and Winrock International for granting access to data and study sites • ARS/USDA for financial support